CEA LETI Minatec Campus, Grenoble, France.
IEEE Trans Ultrason Ferroelectr Freq Control. 2011 Dec;58(12):2516-20. doi: 10.1109/TUFFC.2011.2114.
A phenomenological approach is developed to identify the physical parameters causing the dc-voltage-induced tunability of aluminum nitride (AlN) acoustic resonators, widely used for RF filters. The typical resonance frequency of these resonators varies from 2.038 GHz at -200 V to 2.062 GHz at +200 V. This indicates, based on these RF measurements versus dc bias and the model used, that the AlN stiffness variation versus dc bias is the prominent effect because both resonance and antiresonance experience a similar variation, respectively, 24 MHz and 19 MHz at 400 V. Picosecond ultrasonics were also used to prove independently that the acoustic velocity (and therefore AlN stiffness) is sensitive to dc bias and that the variation induced is comparable to that extracted from the resonance measurements. It turned out that the stiffness relative variation for an electric field of 1 V/μm extracted from picosecond ultrasonics is 54 ppm-μm/V. This is in good agreement with the value extracted from the RF measurements, namely 57.2 ppm-μm/V. The overall tunability of these AlN resonators reaches 1.1%, which is an interesting figure, although probably not high enough for genuine applications.
采用现象学方法来确定导致氮化铝（AlN）声谐振器的直流电压可调性的物理参数，这些声谐振器广泛用于射频滤波器。这些谐振器的典型共振频率在-200V 时为 2.038GHz，在+200V 时为 2.062GHz。这表明，根据这些 RF 测量值与直流偏置以及所使用的模型，AlN 硬度随直流偏置的变化是主要影响因素，因为共振和反共振都经历了类似的变化，在 400V 时分别为 24MHz 和 19MHz。皮秒超声也被用于独立证明声速（因此 AlN 硬度）对直流偏置敏感，并且诱导的变化与从共振测量中提取的变化相当。结果表明，从皮秒超声中提取的每微米 1V 电场的刚度相对变化为 54ppm-μm/V。这与从 RF 测量中提取的值（即 57.2ppm-μm/V）非常吻合。这些 AlN 谐振器的整体调谐率达到 1.1%，这是一个有趣的数字，尽管可能不足以满足真正的应用需求。
